A referendum on whether the District should adopt mandatory sentencing for certain crimes will face District voters when they go to the polls Tuesday.

The measure, listed on the ballot as initiative 9, would require judges to impose mandatory prison terms for most persons convicted of using a firearm in a violent crime and for certain drug offenses.

The question, the ninth initiative proposal here since voters approved that procedure in 1977, was placed on the ballot after supporters of the measure collected more than 24,000 citizens' signatures. The campaign for the proposed new law has been led by D. C. City Council member and may oral candidate John Ray (D-At Large), who helped draft the measure, and by citizens for Safer Streets, a group headed by former D. C. police chief Burtell Jefferson.

Last week, the National Rifle Association publicity gave its support ot the proposal and sent its members out to distribute more than 50,000 pamphlets that read "Vote Prison Time for Violent Crime."

Initiative 9 is opposed by most of the city's political Leaders, the U.S. attorney (who is the city's top criminal prosecutor), major civil rights groups, civil liberties organizations and a citizens' coalition called Citizens for Sensible Sentencing.

Nevertheless, a recent poll of registered voters showed 71 percent supported the measure, 17 percent opposed it and 12 percent were undecided.

Budgets have been very lean on both sides of the campaign, with recent efforts focusing on radio talk shows and neighborhood forums. Citizens for Safer Streets reported last week that it has spent less than $3,000 on the campaign, while citizens for Sensible Sentencing spent under $2,000.

Yesterday, Ray stood in front of the Northwest Washington home of two brothers who were fatally shot last summer and urged passage of the measure, which he called an "important tool" in the fight against crime. Opponents are expected to canvass local churches today in hopes of persuading voters to defeat the initiative.

Here are some of the major questions and answers about the issue:

What is a mandatory-minimum prison sentence?

It means that for persons convicted of certain crimes, a judge will have no choice but to impose a minimum prison term specified by Law. For example, under the new law, if a first offender is convicted of, or pleads guilty to, armed robbery, the judge must sentence him to serve at least five years in jail, with no chance for parole or probation. The judge could sentence that defendant to a longer prison term, but a flat minimum of five years would have to be served before there was any possibility of release.

Who would be subject to mandatory prison terms?

The new law would apply only to persons convicted of committing a violent crime with a firearm and those convicted of the sale or distribution of certain categories of controlled drugs. Under D.C. law, crimes of violence include murder, rape, robbery, burglary, assault with intent to kill, rape or rob and assault with a dangerous weapon.

Are there any exceptions?

The law would not apply to persons under the age of 22, who are eligible to be sentenced under the terms of the federal Youth Corrections Act. In addition, the mandatory penalties for drug offenses can be avoided if a first offender proves that he is an addict and sold illegal drugs to support that habit.

What are the mandatory penalties?

A personconvicted of committing a crime of violence with a firearm for the first time would be subject to a mandatory term of five years in prison. Repeat offenders would be subject to a mandatory 10-year term.

Persons convicted of sale or distribution of narcotic drugs, such as heroin, would be subject to a mandatory minimum term of four years in jail. Sale of non-narcotic drugs such as cocaine or phencyclidine carries a mandatory term of 20 months upon conviction. A person convicted of selling other kinds of illegal substances, such as marijuana, would be subject to a mandatory term of one year if the drugs to be sold had a street value in excess of $15,000.

Would the new law affect persons convicted of possession of small quantities of drugs?

Proponents of the measure say it was drafted to target drug dealers, not persons convicted of simple possession of small quantities of drugs intended for personal use. Simple possession is a misdemeanor offense under D.C. law.

Do mandatory prison terms deter crime?

As the concept has increased in popularity -- 32 states have some form of mandatory sentencing on the books -- researchers have devoted themselves to studying its effect on crime rates, but the results of their work are mixed. One thing they agree on, however, is that impact of such a law depends on the response to it by the police, prosecutors, judges and corrections officials.

Proponents argue that the value of the new law is that it will make it clear to criminals, especially repeat offenders, that they will face swift and certain punishment if they are convicted of a crime specified in the new law.

The opponents contend that studies have shown that such laws have no discernible effect on crime rates. They contend that mandatory sentencing deprives judges of the discretion they need at the time of sentencing to consider circumstances that would warrant a lesser penalty than those required by the new law.

How much will the new law const?

Opponents of initiative 9 contend the new law could result in an 8- to 10-per cent increase in the prison population, at a cost of $15,000 to $22,000 per prisoner per year.

Supporters of the measure vigorously dispute those projections, arguing that the measure would not adc significantly to the prison population because it is aimed only at two narrow categories of criminals.

What effect would the new law have on the operation of the city's criminal justice system?

The opponents contend that the measure will further tangle up the court system because defendants facing a mandatory prison term will demand to go to trial rather than reach a plea bargain agreement with the prosecutor. They also contend that judges will find ways to circumvent the mandatory penalties if they feel they are not warranted.

Who can vote on initiative 9?

All registered voters, including those registered in the Democratic, Republican and Statehood parties, as well as independents, can vote for or against initiative 9 or Tuesday.

How would the new law take effect?

If the initiative is approved by a majority of the voters Tuesday, it would be sent to Congress for review, as is all routine D.C. Legislation. Unless Congress rejects the measure within 30 days, it would become law.